Humana's ( HUM) second-quarter earnings rose 10% from a year ago and far surpassed Wall Street estimates, thanks to strength in the insurer's Medicare segment. The company issued mixed guidance. Humana earned $89.5 million, or 53 cents a share, in the quarter, up from $81.4 million, or 49 cents a share, a year ago. Analysts surveyed by Thomson First Call had been forecasting earnings of 35 cents a share in the most recent period. Second-quarter revenue rose 53% from last year to $5.41 billion, beating the consensus estimate by $120 million. "The upside in the quarter was a combination of better-than-expected performance in the company's Medicare Advantage, commercial and Tricare business lines, partially offset by profit margins in its Prescription Drug Plans moving to the low end of the projected range," Humana said. At June 30, Humana said, membership in its Medicare Advantage program was 959,000, up 102% from a year earlier. "The company's expanded participation in various Medicare products and markets combined with the company's increased sales and marketing efforts for these programs led to the higher membership level," it said. Humana reiterated full-year profit guidance of $2.82 to $2.88 a share, on revenue of $21 billion to $22 billion. That's in line with the Thomson First Call consensus estimate of $2.80 a share. For the third quarter, Humana sees earnings of 95 cents to $1 a share; analysts were predicting $1.01 a share. "In addition to the impact of changes associated with second-quarter performance, this forecast has been revised to reflect management's updated expectations for Medicare marketing costs in the latter half of 2006," Humana said. "In order to maximize 2007 Medicare growth opportunities, the company now anticipates its second-half 2006 Medicare marketing costs to be approximately $0.15 per share higher than it had previously forecast."